This application claims the priority of German patent document 2990942.9, filed May 27, 1999, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a woof yarn tension device for weaving machines.
German Patent Document DE 34 46 567 C1 discloses a woof yarn tension device with a controllable tensioning effect which consists of two lamella-type parts which are resiliently disposed with respect to one another and receive the woof yarn between one another, guide eyes being arranged at the respective input and output of the woof yarn tension device, which guide eyes, also when the tension device is opened up, represent a constant stress to the woof yarn as the result of friction and deflection. A plurality of other types of yarn tension devices are known, for example, having a tension band and a controllable tension body, between which the woof yarn is guided, or so-called wrap tension devices, in the case of which the tensioning force can be adjusted by changing the angle of wrap.
Woof yarn tension devices of this type are part of an arrangement on the feeding side for the woof yarn, which side consists essentially of the prewinding device, the woof yarn tension device, the woof yarn monitor and the woof yarn presenting device, the woof yarn passing through these devices before the feeding by a corresponding feeding element into the weaving shed. For the alternate feeding of different woof yarns, this arrangement is present several times. The woof yarn tension device, the woof yarn monitor and the woof yarn presenting device have together, as a rule, several deflecting points in the form of yarn guide eyes, through which the woof yarn travels, although at small deviation angles. At the high speeds of the weaving machines customary today, this results in increased friction and therefore a higher stressing of the woof yarn at each deflection point.
For reducing the stressing of the yarn, a device is known from German Patent Document DE 195 35 895 C1 which provides only one common woof yarn monitor for a plurality of woof yarn types to be fed, which woof yarn monitor is brought in contact with the woof yarn to be fed only for a certain time period during the feeding of the woof. Although the described device reduces the duration of the contact between the woof yarn and the woof yarn monitor, it requires high constructive expenditures and, on the whole, does not result in a reduction of the required deflection points.
European Patent Document EP 0 634 509 A1 discloses a woof yarn tension device which is followed by a yarn tension sensor whose measuring values are used for controlling the tensioning force of the woof yarn tension device. As the result, the tensioning force can be optimally adjusted during each woof feeding, which, among other things, reduces the stressing of the woof yarn. This device also has the disadvantage that a total of at least three yarn guide eyes are required and the yarn tension sensor has additional deflection points for the mechanical sensing of force, whereby the overall stressing of the woof yarn is increased further.
From European Patent Document EP 0 333 302 A1, it is known to arrange, in a woof yarn feeding system of a gripper weaving machine, a separate monitor for the woof yarn behind the woof yarn tension devices (tandem tension devices) in the woof feeding direction. For the plurality of the woof yarns travelling through the woof monitor, the corresponding woof monitor represents a deflection point, although at a small angle. This deflection results in friction and therefore in an undesirable stressing of the yarn.
It is an object of the invention to further develop a woof yarn tension device with a yarn guide eye on the output side such that the stressing of the woof yarn can be reduced.
According to the invention, this object is achieved by providing a woof yarn tension device for weaving machines, consisting of a controllable tension device which acts upon the woof yarn and which, at least on the output side, has a yarn guide eye, characterized in that the yarn guide eye is constructed as a woof yarn monitor.
The invention is based on the fact that the output-side yarn guide eye of the woof yarn tension device is constructed as a woof yarn monitor.
This results in the important advantage that an additional woof yarn monitor on the output side of the woof yarn tension device can be eliminated, whereby at least one deflection point is eliminated. The reduction of the total number of deflection points results in a lower stressing of the yarn.
Another advantage of the combination of the woof yarn tension device and the woof yarn monitor according to the invention consists of the compact construction and simplified mounting and adjusting of the arrangement on the weaving machine. The type of the used tension device plays no role that would be essential to the invention. According to the invention, all types of the initially mentioned woof yarn tension devices or other types can be equipped with an integrated woof yarn monitor.
Advantageous features and further developments of the invention are described herein and in the claims.
The woof yarn monitor is preferably constructed as a piezo-electric sensor which is integrated in the output-side guide eye of the woof yarn tension device. However, in a known manner, the woof yarn monitor may also contain an electro-mechanical sensor, an electro-optical sensor, a capacitive or an inductive sensor.
The integrated woof yarn monitor can advantageously be constructed as a yarn tension sensor whose output signal is returned to the woof yarn tension device for controlling the tensioning force.
A woof yarn tension device is assigned to one used woof yarn type or one used woof yarn color respectively.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.